1. Field of the Invention
Embodiments of the present invention generally relate to systems and methods for hydrocarbon processing. More particularly, embodiments of the present invention relate to systems and methods for fractionating a multi-component fluid.
2. Description of the Related Art
Distillation columns or fractionators are typically vertical vessels operated at certain conditions and pressures suitable to separate a feed mixture into two or more fractions. Such fractions are typically removed from the top, i.e. the lights and from the bottom of the column, i.e. the heavies. The fractionation of multi-component mixtures having more than two components is typically adapted to remove liquid and gaseous products from the side of the column. However, such side products typically contain proportions of the low-boiling components which are normally taken off at the top and/or proportions of the higher-boiling components which are normally taken off at the bottom. To isolate intermediate-boiling substances from multi-component mixtures, multiple columns are typically used. An advantageous alternative is to use a dividing wall column.
In a dividing wall column, a dividing wall is located within the column. The dividing wall typically extends some distance above and below the side feed entry point of the column. On the side of the dividing wall opposite to the feed introduction point at least one intermediate product draw is located. The dividing wall prevents the lateral mixing of the feed and the fraction removed via the intermediate product draw on the opposite side of the dividing wall. The fraction removed via the intermediate product draw advantageously has a higher concentration of lower boiling point components than similar fractionation or distillation columns operated without the dividing wall. Exemplary dividing wall columns are described in U.S. Pat. Nos. 2,471,134; 5,755,933; 5,914,012; 6,347,533; 6,645,350; and 6,958,111.
A disadvantage of all distillation columns, including dividing wall columns, is that heat recovery from the overhead product is difficult if not impossible. The temperature of the overhead removed from the column is lower than the temperature at the base or bottom of the column. Although recovery of at least a portion of the heat in the overhead is desirable, the temperature of the overhead precludes direct heat exchange with the bottom.
There is a need, therefore, for a dividing wall column and fractionation system using the same that has improved heat recovery.